Pakistani authorities have put rescue services on high alert after heavy rains, thunderstorms and lightning wrought havoc across the country. The National Disaster Management Authority (NDMA) has asked emergency services to be vigilant as more severe weather moves in. The death toll from the heavy rains over the past four days has risen to 50, according to officials from provincial wings of the authority on Tuesday. At least 21 people, including seven children, were killed when lightning struck in central Punjab province. Another 21 people were killed in the north-western province of Khyber Pa…